1. Field of the Invention
The invention relates to tubing expansion. In particular, the invention relates to methods and apparatus for expanding tubulars downhole, especially expanding discrete lengths of tubing downhole.
2. Description of the Related Art
Recently, methods and apparatus have been developed for placing tubular strings in a wellbore and then expanding the inner and outer diameters of the strings in order increase a fluid path through the tubulars and in some cases to line the walls of a wellbore. The advantages of expanding tubulars in a wellbore are obvious. The tubular strings are easier to assemble and run into the wellbore prior to being expanding and are typically less expensive. There are many examples of downhole expansion of tubulars including patents owned by the assignee of the present invention. U.S. Pat. No. 6,457,532 assigned to Weatherford/Lamb, Inc. discloses a number of methods for downhole expansion including an expansion tool which combines compliant and non-compliant expansion means.
In some instances, it is necessary to place a discrete length of tubing in a wellbore either to line a specific area of the bore or for remedial purposes when a section of tubular casing has become damaged. Expanding discrete lengths of tubing in a wellbore is a complicated process because the pre-expanded tubing must be run to depth and held with some other tubular string downhole before and during expansion. Prior art procedures include a method wherein a discrete length of unexpanded tubular is run into a wellbore on a separate, smaller work string and thereafter, using an anchor and an expansion cone, the string is anchored to the wellbore wall and then expanded as the cone is urged upwards or downwards relative to the string.
It is among the objectives of the embodiments of this invention of provide improved and/or additional methods and apparatus for expanding tubulars.